| Marsh Lane Management Limited | Professional & scientific | 1988 |
| Marshall Blue Garden Rooms Ltd | Construction | 2023 |
| Marshall Double Glazing Limited | Manufacturing | 2003 |
| Marsta Properties Limited | Construction | 2011 |
| Martos 1932 Limited | Hospitality | 2018 |
| Marvel Padel Ltd | Arts & recreation | 2025 |
| Masonry Clean UK Limited | Construction | 2022 |
| Masters Fitness & Wellbeing Ltd | Health & social care | 2018 |
| Mathew James Limited | Wholesale & retail | 2025 |
| Matt Garner Consulting Limited | Professional & scientific | 2017 |
| Matthew Parker Advisory Group Ltd | Professional & scientific | 2024 |
| Matthew Swindells Limited | Professional & scientific | 2019 |
| Maurice Global Ltd | Wholesale & retail | 2017 |
| MAX Protection K9 Limited | Wholesale & retail | 2023 |
| Maynards View (Cutlers Green) Management Company Limited | Households | 2023 |
| Maytry Limited | Construction | 2021 |
| MB Beers and Wine Ltd | Wholesale & retail | 2025 |
| MB Bespoke Solutions Ltd | Administrative & support | 2017 |
| MB Dance Academy CIC | Arts & recreation | 2023 |
| MB Tour Coaching Ltd | Education | 2025 |
| MBJ Commercial Limited | Professional & scientific | 2023 |
| Mcallister-Jones Consulting Limited | Professional & scientific | 2026 |
| Mcgowan and Howard Plumbing Solutions Ltd | Construction | 2024 |
| MCP Plus Ltd | Construction | 2025 |
| MCS Building Solutions Ltd | Construction | 2009 |
| Mdls Holdings Ltd | Financial services | 2019 |
| Mdls Property Developments Limited | Construction | 2019 |
| Mdls Property Rental Limited | Real estate | 2019 |
| MDN Homes Ltd | Real estate | 2024 |
| MDS Floorcare Ltd. | Administrative & support | 2006 |
| Mechara Ltd | Other services | 2017 |
| Media Qlique Limited | Administrative & support | 2021 |
| Media Universe Ltd | Information & communication | 2007 |
| MEG Property Management Limited | Real estate | 2012 |
| Melburyrose Limited | Real estate | 2004 |
| Melin Maintenance Limited | Households | 2024 |
| Melo Supplements Limited | Wholesale & retail | 2024 |
| Meridian Holdings (London) Ltd | Real estate | 2026 |
| Merner Investments Limited | Financial services | 2019 |
| Merner Limited | Real estate | 2021 |
| Merner Properties Limited | Real estate | 2020 |
| Mersai Health Clinic Limited | Health & social care | 2014 |
| Metal Frames Ltd | Manufacturing | 2022 |
| Metamorphysis Ltd | Wholesale & retail | 2025 |
| Metisium Ltd | Professional & scientific | 2026 |
| MF Systems Consulting Limited | Information & communication | 2011 |
| MFW GAS and Heating Services Limited | Administrative & support | 2016 |
| MGR Roofing Ltd | Construction | 2022 |
| MH 10 Global Ltd | Other services | 2023 |
| Miahcorp Digital Limited | Manufacturing | 2024 |
| Mianuu Ltd | Arts & recreation | 2025 |
| Michelle Killick Bookkeeping Services Ltd | Professional & scientific | 2023 |
| Midas Plumbing Ltd | Construction | 2023 |
| Midas Touch Assets Limited | Real estate | 2021 |
| Middle Marketing Limited | Professional & scientific | 2025 |
| Midori Ltd | Hospitality | 2025 |
| Midorick Solutions UK Ltd | Professional & scientific | 2026 |
| Migan Hospitality Ltd | Hospitality | 2020 |
| Mighty Media Discs Limited | Information & communication | 2008 |
| Mii-Pro Ltd | Professional & scientific | 2018 |
| Mikenopa UK & Ireland Limited | Information & communication | 2014 |
| Milestone Careers Ltd | Administrative & support | 2020 |
| Militia Brazilian JIU Jitsu Limited | Education | 2022 |
| Miller Coordination Ltd | Construction | 2018 |
| Millfield Essex Limited | Real estate | 2020 |
| Millfield Group Holdings Limited | Financial services | 2026 |
| Millfield Property Rentals Limited | Real estate | 2025 |
| Milnthorp Maintenance Ltd | Administrative & support | 2024 |
| Mimosa Resources Ltd | Real estate | 2020 |
| Mimram and LEA Ltd | Professional & scientific | 2017 |
| Mini Ballers Ltd | Education | 2022 |
| Minimally Invasive Periodontics Ltd | Health & social care | 2017 |
| Minority Ethnic Network Eastern Region | Health & social care | 2000 |
| Mint Hair Ltd | Other services | 2013 |
| Miran Barbers Limited | Other services | 2019 |
| Mispna Properties Limited | Real estate | 2020 |
| Mitre Carpentry Ltd | Construction | 2016 |
| MJR Consultants Ltd | Professional & scientific | 2022 |
| MJR Developments (South East) Ltd | Real estate | 2017 |
| MK Financial Management Ltd | Professional & scientific | 2013 |
| MK2 Developments Limited | Real estate | 2018 |
| Mkdc Consulting Limited | Professional & scientific | 2012 |
| MKT AI Ltd | Administrative & support | 2018 |
| MM Estate Properties Limited | Real estate | 2024 |
| MME Electrical Contractors Limited | Construction | 2004 |
| MMT Design Services Ltd | Arts & recreation | 2017 |
| MMV Autocare Ltd | Wholesale & retail | 2024 |
| Mnrb Group Ltd | Information & communication | 2015 |
| Moat House Management Company Limited | Extraterritorial | 2014 |
| Mode Communications Limited | Other services | 2012 |
| Mode Copiers Limited | Wholesale & retail | 2011 |
| Mode IT Solutions Limited | Wholesale & retail | 2015 |
| Mode Lighting (UK) Limited | Extraterritorial | 1976 |
| Mode Print Solutions Limited | Professional & scientific | 2022 |
| Mode Solutions Limited | Professional & scientific | 2015 |
| Mojo Nation Ltd | Administrative & support | 2017 |
| Moles Farm Barns Ltd | Households | 2024 |
| Monica Court (Freehold) Limited | Households | 2005 |
| Monica Court Residents' Association Limited | Households | 1984 |
| Monks ROW RTM Company Limited | Households | 2009 |